Axial flux motors and generators are known in the art. In such machines, a stator assembly is interposed between two magnets magnetized with alternating north-south poles. These magnets are affixed to a rotor shaft via a back iron assembly for connection to a mechanical load (or source for a generator). An example of such an axial flux motor/generator is described in U.S. Pat. No. 7,109,625 (“the '625 patent”), which is incorporated herein by reference in its entirety.
A known assembly procedure for affixing a ring magnet to a back iron assembly for use in such an axial flux motor involves several steps, which are illustrated in FIGS. 1-3. First, as shown in FIG. 1, a ring magnet 102 with the desired magnetic field pattern is lowered in a controlled fashion over a cylindrical shaft 104 to a steel transfer plate 106 (e.g., by reducing the height of push-off pins 108) where it is held firmly by magnetic force.
Then, as illustrated in FIG. 2, a back iron assembly 110 is lowered to the exposed side of the ring magnet 102, using the transfer plate 106 to hold the ring magnet 102 in place. Finally, as shown in FIG. 3, to release the back iron assembly 110 and ring magnet 102 from the transfer plate 106, ejector pins 112 are extended to separate and consequently reduce the force of attraction between the ring magnet 102 and transfer plate 106. The back iron assembly and magnet 102 together form a rotor assembly 114 that can be used, for example, in an axial flux motor or generator such as that described in the '625 patent.
A bottom view of a rotor assembly 114 resulting from the foregoing technique is shown in FIG. 4. As shown, in the rotor assembly 114, the magnet 102 is held in place within the back iron assembly 110 by a combination of magnetic force and/or adhesives. During the assembly operation, care is generally taken to control the transfer from one surface to another to avoid damaging or breaking magnets.
The motors/generators described in the '625 patent employ two rotor assemblies 114 such as that as shown in FIG. 4. The ring magnets 102 of the rotor assemblies 114 are magnetized so that they present an alternating sequence of north and south poles as a function of angle. Those assemblies are mounted on a rotor shaft on either side of a planar stator, and are oriented so that the north poles on one assembly correspond to and face the south poles on the opposing assembly. In some cases, rotor assemblies 114 have been assembled to a rotor shaft of a motor or generator using an adhesive product, such as LOCTITE.